Thanks for signing up! You might also like these other newsletters:

There are five types of psoriatic arthritis, affecting different parts of the body.

Getty Images

Psoriatic arthritis varies from person to person, and the difference isn’t just a matter of severity.

There are five subtypes of psoriatic arthritis, based on which parts of the body are affected. You can also have one type of psoriatic arthritis and then develop a different subtype down the road.

“The categories tend to bleed into each other,” says Anca Askanase, MD, a rheumatologist and associate professor of medicine at the Columbia University Medical Center in New York City. “Ultimately, they’re all about joint pain, stiffness, and loss of function.”

Knowing which type of psoriatic arthritis you have can help inform your treatment and perhaps your prognosis. The systemic, or whole-body, and biologic drug treatments are similar for these types, but the approach to flare-ups may vary, Dr. Askanase notes.

Here’s a look at the different types of psoriatic arthritis:

Symmetric Psoriatic Arthritis

Just as rheumatoid arthritis tends to affect the same joints on opposite sides of the body, symmetric psoriatic arthritis can follow a similar pattern, says Kathy McKinnon, DO, a senior staff physician at Henry Ford Health System and an associate professor of medicine at Wayne State University in Detroit.

With symmetric psoriatic arthritis, the exact same joints aren’t necessarily affected. While joints in the fingers of the right and left hands may be affected simultaneously, the joints closest to your fingertips might be affected on the right hand, while the joints closest to the base of the fingers might be affected on the left, or vice versa, for example. This type, which makes up about 33 percent of psoriatic arthritis cases, can also affect the knees, wrists, and ankles.

Asymmetric Psoriatic Arthritis

This is the most common subtype, accounting for 43 percent of cases of psoriatic arthritis, according to research published in the journal Rheumatology. While asymmetric psoriatic arthritis can occur in any joint, it doesn’t affect the same joints on both sides of the body.

When it affects the fingers and toes, the swelling and redness can make them look like small sausages (known as dactylitis). Even though fewer joints may be affected, given the lack of symmetry, the intensity can be disabling and difficult to treat, Askanase says. For acute flare-ups, steroid injections, NSAIDs, and physical therapy can help.

Distal Psoriatic Arthritis

This type is usually a milder version and not as damaging to functionality, Askanase says. It affects the “distal” joints, meaning it causes inflammation and stiffness in the small joints that are closest to the nails on your fingers and toes. Since these joints are so close to the nails, symptoms can include spotting or pitting in the nails or a lifting of the nail from the nail bed.

Spondylitis

Pain, inflammation, and stiffness in the neck, spine, and sacroiliac joints — which are between the sacrum, the bone connected to your tailbone, and the pelvis — are the telltale signs of this psoriatic arthritis subtype.

“The big concern is this disease can progress relentlessly and lead to severe, incapacitating damage to the spine,” Askanase says. The end result can cause significant impairments in mobility and functionality. “TNF inhibitors [a type of biologic therapy that blocks a protein called tumor necrosis factor alpha, or TNF-alpha] have made a huge difference in our ability to control pain and provide continuous functionality in early stages [of spondylitis],” Askanase notes.

Only 4 percent of people with psoriatic arthritis have spondylitis as their primary symptom.

Arthritis Mutilans

A relatively rare subtype, arthritis mutilans can cause serious damage and deformity to the joints in the hands and feet. It can affect other parts of the body, such as the neck and back, too.

“It may not be as noisy in terms of pain and stiffness, yet the end result is quite extraordinary because of the amount of damage it causes,” Askanase says. The most common forms of damage include bone loss, telescoping of the fingers (in which the fingers lose bone and soft tissues can’t hold the fingers up), and shortening of the fingers, according to a study published in August 2015 in the Journal of Rheumatology.